
static CRC16_TAB: &'static [u16; 256] = &[0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6,
                                          0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad,
                                          0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5,
                                          0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a,
                                          0xd3bd, 0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420,
                                          0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b,
                                          0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 0x3653,
                                          0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
                                          0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d,
                                          0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861,
                                          0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948,
                                          0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96,
                                          0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf,
                                          0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87,
                                          0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae,
                                          0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
                                          0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51,
                                          0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a,
                                          0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c,
                                          0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3,
                                          0x5004, 0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb,
                                          0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290,
                                          0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea,
                                          0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
                                          0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424,
                                          0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e,
                                          0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657,
                                          0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f,
                                          0x99c8, 0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806,
                                          0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c,
                                          0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75,
                                          0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
                                          0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8,
                                          0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83,
                                          0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b,
                                          0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74,
                                          0x2e93, 0x3eb2, 0x0ed1, 0x1ef0];


pub fn crc16(bytes: &[u8]) -> u16 {
    let mut crc: u16 = 0;
    for counter in 0..bytes.len() {
        let index = (((crc >> 8) as u8) ^ bytes[counter]) & 0xFF;
        let value = CRC16_TAB[index as usize];
        crc = (crc << 8) ^ value;
    }
    crc
}

// We have 16384 hash slots. The hash slot of a given key is obtained
// as the least significant 14 bits of the crc16 of the key.
//
// However if the key contains the {...} pattern, only the part between
// { and } is hashed. This may be useful in the future to force certain
// keys to be in the same node (assuming no resharding is in progress).
pub fn key_hash_slot(bytes: &[u8]) -> u16 {
    let mut s = 0; /* start-end indexes of { and } */
    let keylen = bytes.len();
    while s < keylen {
        if bytes[s] == b'{' {
            break;
        }
        s += 1;
    }
    if s == keylen {
        return crc16(bytes) & 0x3FFF;
    }
    let mut e = s + 1;
    while e < keylen {
        if bytes[e] == b'}' {
            break;
        }
        e += 1;
    }
    if e == keylen || e == s + 1 {
        return crc16(bytes) & 0x3FFF;
    }
    crc16(&bytes[(s + 1)..e]) & 0x3FFF
}
